title: Sox2 suppresses the invasiveness of breast cancer cells via a mechanism that is dependent on Twist1 and the status of Sox2 transcription activity.
abstract: BACKGROUND
  Sox2, an embryonic stem cell marker, is aberrantly expressed in a subset of breast cancer (BC). While the aberrant expression of Sox2 has been shown to significantly correlate with a number of clinicopathologic parameters in BC, its biological significance in BC is incompletely understood.
  
  
  METHODS
  In-vitro invasion assay was used to evaluate whether the expression of Sox2 is linked to the invasiveness of MCF7 and ZR751 cells. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and/or Western blots were used to assess if Sox2 modulates the expression of factors known to regulate epithelial mesenchymal transition (EMT), such as Twist1. Chromatin immunoprecipitation (ChIP) was used to assess the binding of Sox2 to the promoter region of Twist1.
  
  
  RESULTS
  We found that siRNA knockdown of Sox2 expression significantly increased the invasiveness of MCF7 and ZR751 cells. However, when MCF7 cells were separated into two distinct subsets based on their differential responsiveness to the Sox2 reporter, the Sox2-mediated effects on invasiveness was observed only in 'reporter un-responsive' cells (RU cells) but not 'reporter responsive' cells (RR cells). Correlating with these findings, siRNA knockdown of Sox2 in RU cells, but not RR cells, dramatically increased the expression of Twist1. Accordingly, using ChIP, we found evidence that Sox2 binds to the promoter region of Twist1 in RU cells only. Lastly, siRNA knockdown of Twist1 largely abrogated the regulatory effect of Sox2 on the invasiveness in RU cells, suggesting that the observed Sox2-mediated effects are Twist1-dependent.
  
  
  CONCLUSIONS
  Sox2 regulates the invasiveness of BC cells via a mechanism that is dependent on Twist1 and the transcriptional status of Sox2. Our results have further highlighted a new level of biological complexity and heterogeneity of BC cells that may carry significant clinical implications.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Fang
authors.initials: F
authors.lastname: Wu
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Ye
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Karen
authors.initials: K
authors.lastname: Jung
authors.forename: Chengsheng
authors.initials: C
authors.lastname: Wu
authors.forename: Donna
authors.initials: D
authors.lastname: Douglas
authors.forename: Norman
authors.initials: N
authors.lastname: Kneteman
authors.forename: Gilbert
authors.initials: G
authors.lastname: Bigras
authors.forename: Yupo
authors.initials: Y
authors.lastname: Ma
authors.forename: Raymond
authors.initials: R
authors.lastname: Lai
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006801:Humans; D009361:Neoplasm Invasiveness / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055748:SOXB1 Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D051879:Twist-Related Protein 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; C103173:TWIST1 protein, human; D051879:Twist-Related Protein 1